The interface used for the custom mapping of an SQL user-defined type (UDT) to a class in the Java programming language. The class object for a class implementing the
SQLData
interface will be entered in the appropriate
Connection
object's type map along with the SQL name of the UDT for which it is a custom mapping.
Typically, a SQLData
implementation will define a field for each attribute of an SQL structured type or a single field for an SQL DISTINCT
type. When the UDT is retrieved from a data source with the ResultSet.getObject
method, it will be mapped as an instance of this class. A programmer can operate on this class instance just as on any other object in the Java programming language and then store any changes made to it by calling the PreparedStatement.setObject
method, which will map it back to the SQL type.
It is expected that the implementation of the class for a custom mapping will be done by a tool. In a typical implementation, the programmer would simply supply the name of the SQL UDT, the name of the class to which it is being mapped, and the names of the fields to which each of the attributes of the UDT is to be mapped. The tool will use this information to implement the SQLData.readSQL
and SQLData.writeSQL
methods. The readSQL
method calls the appropriate SQLInput
methods to read each attribute from an SQLInput
object, and the writeSQL
method calls SQLOutput
methods to write each attribute back to the data source via an SQLOutput
object.
An application programmer will not normally call SQLData
methods directly, and the SQLInput
and SQLOutput
methods are called internally by SQLData
methods, not by application code.